The present invention relates to laboratory technology and in particular to a method of analysis where in a porous, sheet-like material, such as filter paper, there is absorbed a sample, such as a specimen of dried blood, of which material there is cut a disk, which disk is then conveyed to a vessel or a vessel matrix, such as a set of test tubes or cuvettes, where the sample disk is eluted. After elution, the sample disk can be removed, and the obtained solution is subjected to the analysis in question.
In the above described tasks for conveying a sample disk into a reaction vessel and for removing it therefrom, there are generally used a pair of tweezers, and the method requires a lot of manual work. The analyses are usually carried out in series, for instance on a microtitration plate, in which case the analysis is made simultaneously in each well of the plate. The U.S. patent publication 5,474,742 introduces an apparatus whereby sample disks can be simultaneously inserted in and removed from all wells on the plate. The apparatus comprises a framework with arms for each well, and the bottom part of each arm is provided with a shelf-like sample disk retainer.
The method and apparatus according to the invention is designed to facilitate and speed up the conveying of samples of the described type in and out of the vessel of analysis.
We have now invented a method and apparatus according to the independent claims. Other claims represent a few preferred embodiments of the invention.
According to the invention, a sample disk is attached to a tooth, where it is conveyed to the reaction vessel. The sample disk can also be removed from the vessel by the tooth. One rack may contain several teeth, corresponding to the pitch of the cuvettes provided in the plate used in the analysis, which further facilitates the task of performing several analyses in series.
A tooth may include a sharp, cutting part, in which case the tooth penetrates the sheet with as little damage as possible. Moreover, the tooth may include barbs in order to improve the grip.
A sample disk can be cut of a larger sheet, for instance by punching it directly onto the tooth. In this fashion, less steps are needed in the process. The punching is advantageously carried out by pushing the punching tool downwardly, against the sample sheet.
The apparatus may include means for shifting the tooth rack, preferably automatically, for the length of a tooth interval at a time. The apparatus may also include means for ensuring an accurate position for the shifted rack.
In order to shift the rack, it may contain a suitable grip member, such as an indentation.
A combined sample disk punching and fastening can be realized by means of separate actuators, or by means of one and the same actuator.